The present invention relates to an analog-to-digital converting device and related method, and more particularly to an ADC with filtering functionality and related method.
In a wireless communication system, an analog-to-digital converter (ADC) is used to convert an analog signal into a digital signal after the RF signal is received by an antenna. However, the antenna may also receive signals other than the wanted signal at the same time. Therefore, a filter is used to filter out the unwanted signal before the signal inputting to the ADC. Normally, a filter has larger area or larger power consumption also has better filtering effect, but this also means that the filter costs higher. If a filter having bad filtering effect is employed, then the ADC should have wider dynamic range such that the unwanted signal can be suppressed by the ADC. However, the dynamic range of the ADC is inversely proportional to the supply voltage of the ADC, and the supply voltage only becomes smaller in the modern semiconductor process. Another way to increase the dynamic range of the ADC is to reduce the noise floor of the ADC. However, this method may again increase the area and power consumption of the ADC because the ADC may be designed to have large capacitor and small resistor. Therefore, providing a filtering ADC for cost/area reduction is an urgent problem in the field of wireless communication system.